Method of inhibiting cathepsin K

Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving hydrolase

Reexamination Certificate

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C435S226000, C702S027000

Reexamination Certificate

active

06274336

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method of inhibiting cathepsin K by administering compounds with certain structural, physical and spatial characteristics that allow for the interaction of said compounds with specific residues of the active site of the enzyme. This interaction between the compounds of this invention and the active site inhibits the activity of cathepsin K and these compounds are useful for treating diseases in which said inhibition is indicated, such as osteoporosis and periodontal disease. This invention also relates to a novel crystalline structure of cathepsin K, the identification of a novel protease catalytic active site for this enzyme and methods enabling the design and selection of inhibitors of said active site.
BACKGROUND OF THE INVENTION
Cathepsin K is a member of the family of enzymes which are part of the papain superfamily of cysteine proteases. Cathepsins B, H, L, N and S have been described in the literature. Recently, cathepsin K polypeptide and the cDNA encoding such polypeptide were disclosed in U.S. Pat. No. 5,501,969 (called cathepsin O therein). Cathepsin K has been recently expressed, purified, and characterized. Bossard, M. J., et al., (1996)
J. BioL Chem
. 271, 12517-12524; Drake, F. H., et al., (1996)
J. BioL Chem
. 271, 12511-12516; Bromme, D., et al., (1996)
J. BioL Chem
. 271, 2126-2132.
Cathepsin K has been variously denoted as cathepsin O, cathepsin X or cathepsin O2 in the literature. The designation cathepsin K is considered to be the more appropriate one (name assigned by Nomenclature Committee of the International Union of Biochemistry and Molecular Biology).
Cathepsins of the papain superfamily of cysteine proteases function in the normal physiological process of protein degradation in animals, including humans, e.g., in the degradation of connective tissue. However, elevated levels of these enzymes in the body can result in pathological conditions leading to disease. Thus, cathepsins have been implicated in various disease states, including but not limited to, infections by pneumocystis carinii, trypsanoma cruzi, trypsanoma brucei brucei, and Crithidia fusiculata; as well as in schistosomiasis malaria, tumor metastasis, metachromatic leukodystrophy, muscular dystrophy, amytrophy, and the like. See International Publication Number WO 94/04172, published on Mar. 3, 1994, and references cited therein. See also European Patent Application EP 0 603 873 A1, and references cited therein. Two bacterial cysteine proteases from P. gingivallis, called gingipains, have been implicated in the pathogenesis of gingivitis. Potempa, J., et al. (1994)
Perspectives in Drug Discovery and Design,
2, 445-458.
Cathepsin K is believed to play a causative role in diseases of excessive bone or cartilage loss. Bone is composed of a protein matrix in which spindle- or plate-shaped crystals of hydroxyapatite are incorporated. Type I Collagen represents the major structural protein of bone comprising approximately 90% of the structural protein. The remaining 10% of matrix is composed of a number of non-collagenous proteins, including osteocalcin, proteoglycans, osteopontin, osteonectin, thrombospondin, fibronectin, and bone sialoprotein. Skeletal bone undergoes remodeling at discrete foci throughout life. These foci, or remodeling units, undergo a cycle consisting of a bone resorption phase followed by a phase of bone replacement.
Bone resorption is carried out by osteoclasts, which are multinuclear cells of hematopoietic lineage. The osteoclasts adhere to the bone surface and form a tight sealing zone, followed by extensive membrane ruffling on their apical (i.e., resorbing) surface. This creates an enclosed extracellular compartment on the bone surface that is acidified by proton pumps in the ruffled membrane, and into which the osteoclast secretes proteolytic enzymes. The low pH of the compartment dissolves hydroxyapatite crystals at the bone surface, while the proteolytic enzymes digest the protein matrix. In this way, a resorption lacuna, or pit, is formed. At the end of this phase of the cycle, osteoblasts lay down a new protein matrix that is subsequently mineralized. In several disease states, such as osteoporosis and Paget's disease, the normal balance between bone resorption and formation is disrupted, and there is a net loss of bone at each cycle. Ultimately, this leads to weakening of the bone and may result in increased fracture risk with minimal trauma.
The abundant selective expression of cathepsin K in osteoclasts strongly suggests that this enzyme is essential for bone resorption. Thus, selective inhibition of cathepsin K may provide an effective treatment for diseases of excessive bone loss, including, but not limited to, osteoporosis, gingival diseases such as gingivitis and periodontitis, Paget's disease, hypercalcemia of malignancy, and metabolic bone disease. Cathepsin K levels have also been demonstrated to be elevated in chondroclasts of osteoarthritic synovium. Thus, selective inhibition of cathepsin K may also be useful for treating diseases of excessive cartilage or matrix degradation, including, but not limited to, osteoarthritis and rheumatoid arthritis. Metastatic neoplastic cells also typically express high levels of proteolytic enzymes that degrade the surrounding matrix. Thus, selective inhibition of cathepsin K may also be useful for treating certain neoplastic diseases.
Surprisingly, it has been found that a broad, structurally diverse series of compounds have common structural, physical and spatial characteristics that allow for the interaction of said compounds with specific residues of the active site of cathepsin K and are useful for treating diseases in which inhibition of bone resorption is indicated, such as osteoporosis and periodontal disease. Thus, this invention relates to the method of inhibiting cathepsin K using compounds having the characteristics hereinbelow defined.
SUMMATY OF THE INVENTION
In one aspect, the present invention provides a method for inhibiting cathepsin K by administering compounds with certain structural, physical and spatial characteristics that allow for the interaction of said compounds with specific residues of the active site of the enzyme. This interaction inhibits the activity of cathepsin K and, thus, treats diseases in which bone resorption is a factor.
In another aspect, the present invention provides a novel cysteine protease in crystalline form.
In yet another aspect, the invention provides a novel protease composition characterized by a three dimensional catalytic site formed by the atoms of the amino acid residues listed in Table XXIX.
In still another aspect, the invention provides a method for identifying inhibitors of the compositions described above which methods involve the steps of: providing the coordinates of the protease structure of the invention to a computerized modeling system; identifying compounds which will bind to the structure; and screening the compounds or analogs derived therefrom identified for cathepsin K inhibitory bioaotivity.
Other aspects and advantages of the present invention are described further in the following detailed description of the preferred embodiments thereof


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Baldwin et al, Crystal structures of native and inhibited forms . . . PNAS USA. vol. 90, pp. 6796-6800, Jul. 1993.*
Oxender, et al. Protein Engineering. New

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